Spoken word identification involves during a relatively short temporal window the activation of lexical candidates on the basis of the acoustic pattern of a spoken word and the selection of the appropriate lexical candidate among those activated by the input. The spectral and temporal properties of acoustic patterns, however, can be substantially modified by factors such as speaker's voice and speaking rate. Young adults implicitly (automatically) encode the inherent variability of acoustic patterns and use this information to facilitate speech perception. Research evidence is unclear as to whether aging involves an impairment in these abilities. The proposed experiments will examine whether age- related changes in speech perception can be attributed to defective implicit encoding and/or use of phonetically-relevant information (voice characteristics and speaking rate). Hearing-matched young and older adults will serve as subjects to examine age-related changes in speech perception that are independent of deficits in peripheral auditory processes.